This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 2001-292473 filed on Sep. 25, 2001, the entire content of which is incorporated herein by reference.
1. Field of the Invention
This invention generally relates to an occupant determining device for a vehicle seat. More particularly, the present invention pertains to an occupant determining device for a vehicle seat operated based on a tension of a seat belt for determining whether an occupant on the vehicle seat is an adult or a child.
2. Background of the Invention
In case where an occupant sitting on a passenger seat of a vehicle is a child or a child seat is fixed to a seat, an airbag for the passenger seat is prohibited to be deployed according to regulations in the United States. Thus, an occupant determining device for a vehicle seat which can determine whether an occupant sitting on the passenger seat is an adult or the child, or whether the child seat is on the seat has been developed. However, when an occupant on the seat is determined based on a load applied to the seat, it is difficult to distinguish whether the load is due to a total of a weight of the child seat and a load for tightening a seat belt to fix the child seat to the seat, a total weight of the child and the child seat, or an adult seated. Japanese Laid-open Patent Publication No. 2000-127890 discloses a known device for determining an occupant on the seat based on a tension of the seat belt and the load applied to the seat. In this disclosed device, when the tension of the seat belt exceeds a threshold value, it is determined that the child seat is fixed to the seat. When the tension does not exceed the threshold value, it is further determined whether the occupant is an adult or a child based on a detected value of a load sensor. That is, it is determined that the occupant is an adult if the detected value exceeds a threshold value. If the detected value does not exceed the threshold value, it is determined that the occupant is a child.
According to the disclosed device, the tension of the seat belt is used as criteria for determining whether or not the child seat is fixed to the seat. Thus, the seat belt requires to be securely fastened for fixing the child seat to the seat. In addition, a person requires to make sure that the seat belt is securely fastened.
Thus, a need exists for the occupant determining device for the vehicle seat which allows a person fixing the child seat to the seat to make sure by himself/herself that the seat belt is securely fastened.
According to an aspect of the present invention, an occupant determining device for a vehicle seat includes a tension detecting means for detecting a tension of a seat belt, a load detecting means for detecting a load applied to the vehicle seat, a determining means for determining an occupant on the vehicle seat and a tightened state of the seat belt based on either one or both of a detected result of the tension detecting means and the load detecting means, and a display means for displaying a determination result of the tightened state of the seat belt.
According to another aspect of the present invention, when a detected value of the tension detecting means is equal to or greater than a first threshold value, the determining means determines that the occupant on the vehicle seat is in a first state and the seat belt is in a first tightened state. On the other hand, when the detected value of the tension detecting means is less than the first threshold value, the determining means determines that the seat belt is in a second tightened state. In addition, when the determining means determines that the seat belt is in the second tightened state and a detected value of the load detecting means is equal to or greater than a second threshold value, the determining means determines that the occupant on the vehicle seat is in a second state. Further, when the determining means determines that the seat belt is in the second tightened state and the detected value of the load detecting means is less than the second threshold value, the determining means determines that the occupant on the vehicle seat is in the first state.
According to further another aspect of the present invention, the first state includes the state that a child, a child restraint system or no occupant is on the vehicle seat. In addition, the second state includes the state that an adult is on the vehicle seat.
According to still further another aspect of the present invention, the occupant determining device for the vehicle seat comprises a tension detecting means for detecting a tension of a seat belt, a determining means for determining a tightened state of the seat belt based on a detected result of the tension detecting means, and a display means for displaying a determination result of the tightened state of the seat belt.